I read this article writting by Branch Spalding in The Journal of the American Military Institute, Vol. 3, No. 1 (Spring, 1939). I found the thesis very intriguing, so I thought I would share it with all of you.
A multiplicity of historians have dealt with the Battle of Fredericksburg (December 13, 1862). They present it with varying factual emphasis, with some display of divergent sympathies. All concur, however, on certain facts: Lee took up a strong position on the heights south and west of the Rappahannock River, commanding the river plain, with Longstreet's Corp on the left of his line, and Jackson's Corp on the right, Burnside crossed the river and attacked the position with two separate columns; Sumner's Right Grand Division, heavily reinforced by elements of Hooker's Center Grand Division, hit that portion of Longstreet's Corps posted on Marye's Heights, back of the town of Fredericksburg, and was repulsed; somewhat simultaneously, the left column, Franklin's Left Grand Division, moved against that portion of Jackson's line in the vicinity of Hamilton's Crossing, the extreme Confederate right; a relatively small part of the Left Grand Division was employed, and Meade's Division of Reynolds' Corps, finding an interval in the Confederate line, handsomely drove through and penetrated to a depth of four hundred yards only to be boxed off, compelled to withdraw and narroly escaped capture or annihilation. By nightfall, the battle was over, and Lee had given the Army of the Potomac another costly lesson with regard to frontal assault of a strong defensive position.
Many writers mention the fact that Jackson's Corps occupied a front of slightly less than two miles, and roughly three brigades constituted the front line (Archer with two regiments of Brockenbrough, Lane, and Pender), the flanks of no one brigade being in contact with those of the next in line. Some of them made no comment of this unusual disposition, or the great depth of line, which the three supporting divisions created. (The Corps strength was 38,944) Other's point to the "coincidence" that the breech between Archer and Lane afforded Meade his great opportunity. Some dwell on the fact that a German officer on Stuart's staff admonished about this condition before the battle. Some speak of it as a serious mistake. Most of them agree that it represents an oversight. One points to the piecemeal arrival of the corps and exigency of the situation. A.P. Hill, 12,978 strong, arrived at 10:00 A.M., December 12. Taliaferro came up by noon. During the night on December 12, and early morning of the thirteenth, Early's and D.H. Hill's Divisions came on the field. This is not an excessive time lapse of delivery of all units of a corps of some thirty-nine thousand men. Since the attack did not begin until 10:00 A.M. on the thirteenth, time was ample for closing the intervals in the front of the line with units of A.P. Hill's or Taliaferro's divisions. Argument could scarcely be supported that these dispositions were compelled by the exigency of time and the presence of the enemy. The presence of an enemy, a mile or more distant, and not yet deployed for attack, was no immediate threat in this sense.
It is a remarkable fact that not one of the historians suggests that this strange tactical disposition was deployed by Jackson deliberately and with a design, or calls attention to the striking similarity between Jackson's formation and what is known in modern warfare as a flexible defense.
On the front of thirty-three hundred yards, Jackson's first line was occupied by three brigades of A.P. Hill's Division. On the right was Archer's Brigade and two regiments of Brockenbrough. In the center was Lane's Brigade, an interval of six hundred years occuring between Lane and Archer. On the left and sharply refused, after another interval of six hundred yeards, was Pender's Brigade. Lane's position was well in advance of Archer's and Pender's. Thus the intervals were both front and lateral for Lane; and one can readily understand the perturbation his report indicates tha the felt before the attack. The aggregate strength of those front line units was approximately seventy-nine hundred.
On the wooded high ground behind each of the intervals was posted a brigade along a military road four hundred to six hundred yards in the rear. Gregg covering the right interval, and Thomas the left. Behind Gregg, and supporting the right, was Early's entire Divisipn; and behind Thomas, Taliaferro's Division. In general reserve was the large division of D.H. Hill (10,161 aggregate). Thus a thinly-manned front line (the garrison posted in three isolated units), was supported by deeply massed reserves, concealed in a forest and on a height. The force occupying the front line totaled seven-nine hundred men, while supports massed behind it totaled thirty-one thousand men and made a one mile depth of line. There were better than eleven men per yard of front.
In an age of close-order deployment and mass-line defense, here was an alluring invitation to an attacking force -- but the kind of invitation the spider extended to the fly. All that the attacker had to do was march straight for one of those two wide intervals (approximately six hundred yards each), taking as they advance a terrific cross fire of artillery and direct muskety, and the defensive line would be cracked. After they had penetrated to a suitable depth, Stonewall Jackson would do the rest with that dense reserve of sixteen brigades masked in the thicket. He would box and butcher them. And that is precisely what happened to Meade's Division. It was an invitation to a Cannae.